JPH02182316A - Grooving method for inside face of metal tube - Google Patents

Abstract

PURPOSE:To prevent the generation of defects on the bottom and slant of groove independently of any dimension of metal tube and any shape and dimension of inside grooves by grooving the inside surface while pressing the tube with a grooved plug and rolling member from the part at which the inside diameter part is brought into contact with the approach part of grooved plug. CONSTITUTION:The metal tube 1 is reduced its diameter with a drawing die 2 and a floating plug 3. Then the metal tube 1 is enlarged its diameter and is grooved its inside surface with the rolling member and the grooved plug 4 supported by a retaining ring 7. And then the metal tube 1 is finished its diameter with a diameter finishing die 8 and the enlargement of tube and drawing are performed continuously. In that case, the grooved plug with the approach part in front is used as the grooved plug 4. When the inside surface of the metal tube is enlarged and is grooved in cooperation with these grooved plugs and the rolling member 6, the inside surface is grooved while pressing it with the rolling member 6 together from the part at which the inside diameter part of the metal tube 1 is brought into contact with the approach part of the grooved plug.

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for forming internal grooves on metal tubes such as copper and aluminum used as heat exchanger tubes for heat exchangers in air conditioners and refrigerators. (A section that tries to solve conventional technology! In recent years, air conditioners,
Metal tubes made of copper, aluminum, etc. with internal grooves are used as heat transfer tubes for heat exchangers such as refrigerators, and there are various types of metal tubes with internal grooves of various shapes. It has been demanded. Conventionally, the manufacturing method of internally grooved tubes that can be cut is known as
As disclosed in No. 4-37059, No. 55-103215, etc., there is a rolling pressure drawing method as one of the so-called tube shrinking groove forming methods in which grooves are formed on the inner surface of a processed metal tube while shrinking it. There is. As shown in FIG. 15, this tube shrinking compaction method involves gripping the tip of the metal tube 21 with a chuck and pulling it out, while pressing the metal tube 21 from the outside with a hole die 22 and a floating plug 23 to reduce the diameter. 1. Next, the inner surface of the metal tube 21 is pressed against the grooved plug 25, which has been installed in the tube in advance, using rolling rolls or rolling balls 24 arranged around the outer periphery of the metal tube 21, thereby forming grooves 26 on the inner surface of the tube. It is. However, in this method, the rotating rolling rolls or rolling balls 24 are attached to the metal tube 21 in the area where the grooved plug 25 is located.
Since the groove processing is performed by reducing the inner and outer diameters of the metal tube 21 by pressing the metal tube 21 to Immediately after passing through this section, a compression reaction force acts on this section, which causes a floating phenomenon and tends to distort the metal tube 21. As a result, when the groove of the metal tube previously formed during grooving is pressed against the grooved plug by the next rolling roll or rolling ball, the groove pitch of the metal tube and the grooved plug may be mismatched (splitting). metal pipe 2).
There is a high possibility that internal defects will occur in 1. Furthermore, the metal tube 21 having an inner diameter larger than the outer diameter of the grooved plug 25 is reduced in diameter and compacted with a rolling roll or rolling ball 24, and is pushed into the groove of the grooved plug 25 to perform groove processing. As a result, the metal flow becomes uneven in the groove and groove crest of the grooved plug, causing defects (fin flaws, groove bottom flaws) on the slope and bottom of the groove of the workpiece. There was a problem with how easy it was. For this reason, when used as a heat transfer tube, there were problems such as a decrease in pressure resistance, a decrease in vibration fatigue strength, generation of metal powder, and generation of slow leakage of refrigerant due to brazing defects. In order to eliminate the disadvantages of the pressure drawing method using the tube contraction method, the so-called tube expansion rolling method was proposed, in which the inner surface of the metal tube is grooved while expanding its diameter, as shown in Figure 13. (Patent Application No. 169571/1982). This tube expansion and compaction method involves reducing the diameter of a metal tube 1 with a first die 2 and a floating plug 3, and then expanding the metal tube with a grooved plug 4 having an outer diameter larger than the inner diameter of the metal tube. This method creates grooves on the surface. In addition, in the figure, 1
is an annealed metal tube such as copper or copper alloy to be processed, 2 is a first die with a fixed exit hole diameter, 3 is a floating plug that does not have a bearing part, and 4 is a tie rod 5 and a thrust bearing attached to this floating plug 3 A grooved plug rotatably connected at a grooved plug 4, and a rolling member (rolling ball or rolling roller) 6 that revolves while rotating is arranged on the outer surface of the metal tube at a location corresponding to the grooved plug 4. The rolled member 6 is supported by a retaining ring 7. Further, a diameter adjusting die 8 is arranged behind the rolling member 6. However, with this tube expansion rolling method, both fin flaws and groove bottom defects can be significantly reduced compared to the tube shrinking rolling method.
There has been a problem in that defects on groove slopes (fin defects) often occur. The present invention has been made in order to eliminate the drawbacks of the prior art regarding the above-mentioned tube expansion and rolling method. Regardless of the dimensions of the metal tube and the shape and dimensions of the inner groove, defects do not occur, especially on the groove bottom and groove slope. It is an object of the present invention to provide a method for producing high quality internally grooved tubes. (Means for Solving the Problems) In order to achieve the above object, the inventor of the present invention has conducted intensive research to investigate the cause of the above drawbacks caused by the conventional system and to find a solution to the problem. First, we focused on metal flow as the groove formation mechanism during grooving in the conventional tube contraction rolling method and tube expansion rolling method, and endeavored to elucidate the cause of the above-mentioned defects occurring in the tube expansion rolling method as well. As a result, in the case of the tube reduction compaction method, as shown in Fig. 1, the grooved plug rotates in the direction of the arrow in the figure (counterclockwise), and the rolled ball rotates in the direction of the arrow in the figure (in the paper). Grooves are formed by compressing the metal tube against the grooved plug while reducing its diameter with a rolling ball while the metal tube is rotating and revolving at right angles (to the right). At this time, the metal in the metal tube flows as if being rolled up toward the bottom of the grooved plug, as shown by the arrow in the figure. The metal flows collide with each other, and the unpressed portion remains on the side surface of the groove, causing a defect (fin defect) on the slope of the inner groove. In addition, since the metal of the metal tube is forcibly reduced in diameter by the rolling balls, the metal on the inner surface of the tube is deformed into wrinkles, which are then compressed by the rolling balls against the groove ridges of the grooved plug. Then, it appears as a groove bottom flow at the bottom of the inner groove. This wrinkle-like defect becomes more noticeable as the degree of diameter reduction increases, that is, as the compressive stress acting on the tube increases. Incidentally, as is clear from the micrograph in Figure 2, fairly deep fin flaws have occurred as shown in Figure 2 (a), groove bottom flow has occurred as shown in Figure 2 (b), and metal Demonstrates the relationship between flow conditions and their defects. On the other hand, in the case of the tube expansion rolling method, the grooved plug and rolling ball are in a state of rotation or revolution as in the case of the tube contraction rolling method, but the metal pipe is expanded from the grooved plug approach part. When configured in this position, the grooved plug is expanded at the approach part and simultaneously pressed against the rolled ball to form a groove.
In other words, since the metal tube is compressed while applying a hoop force, the metal of the metal tube becomes a uniform metal flow and is pushed into the groove of the grooved plug, as shown in Figure 3, and as a result, the groove slope is There is no uncrimped part (fin defect) due to metal entrainment, and there is no wrinkle-like defect at the bottom of the inner groove.In particular, the greater the tensile reaction force inside the metal tube caused by the hoop force, that is, the compression When the stress is large (the tube expansion rate is large), the grooved processing is performed while the metal tube is in close contact with the grooved plug, so the effect is remarkable. Incidentally, as is clear from the micrograph in Figure 4, the metal flow is uniform, there are no fin flaws as shown in Figure 4 (C), and there is no groove bottom flow as shown in Figure 4 (d). Proven. From the above test results, we found that the relative positional relationship between the grooved plug and the rolled ball in the tube expansion rolling method is important in order to prevent defects such as fin flaws and wrinkled groove bottom flow. However, the present invention has been made by conducting repeated experimental research on the conditions under which the positional relationship is appropriate. That is, the method for grooving the inner surface of a metal tube according to the present invention is as follows:
The diameter of the metal tube is reduced using a drawing die and a floating plug, and then the inner surface of the metal tube is expanded and grooved using a rolling member supported by a retaining ring and a grooved plug. In the method for grooving the inner surface of a metal tube in which the diameter of the metal tube is adjusted and then the tube is expanded and rolled and drawn, a grooved plug having an approach portion at the front is used as the grooved plug, and the grooved plug and the rolled member are combined. When processing the inner diameter of the metal tube to expand the diameter and groove the inner surface of the metal tube, the inner diameter of the metal tube is compressed by the rolling member from the region where it contacts the grooved plug approach portion while the inner surface is grooved. This is a characteristic feature. The present invention will be explained in more detail below. (Function) As described above, the present invention provides an internally grooved method that is characterized by regulating the relative positional relationship between a grooved plug and a rolling member (rolling ball, rolling roll, etc.) in a so-called pipe expansion rolling method. It is a processing method. The process of forming internal grooves on a metal tube using the tube expansion and rolling method will first be explained with reference to FIG. A floating plug 3 and a grooved plug 4 connected to the floating plug 3 are inserted into the metal tube 1 from the tube end, and after forming a mouth part on the metal tube 1, the first die 2° is used to expand the tube and adjust the diameter. The material is sequentially passed through a die 8 and pulled out, but the gist of the present invention is to configure the grooved plug and the rolling member in the tube expansion rolling section to have a specific positional relationship during the rolling process. It is something. That is, a grooved plug having an approach portion at the front is used as a grooved plug, but when the grooved plug and the rolling member work together to expand the diameter of the inner surface of the metal tube, the inner diameter of the metal tube is From the part that contacts the grooved plug approach part, the inner surface is grooved while being compressed and expanded with the rolling member. This configuration will be explained below with reference to the drawings. For convenience, the case where the rolled member is a rolled ball will be described. Figures 5 and 6 show the internal grooved state. Figure 5 shows the grooved plug with a groove in a part of the approach part, and Figure 6 shows the state of the grooved plug with a large diameter and thickness. This shows the case where a grooved plug with grooves (approach grooves) is used in the entire approach part is used for a grooved pipe. As shown in Fig. 14, if the groove preforming amount is large for large-diameter, thick-walled materials, if the grooved plug shown in Fig. 5 is used, the inner diameter of the metal pipe will be smaller than that of the grooved plug 4. The material hits the non-grooved portion 10 of the entrance approach. Particularly when manufacturing a grooved tube with a certain twist angle, it becomes impossible to convert the axial load applied to the grooved plug 4 into rotational force. Therefore. The plug will malfunction and the material will not come out and break. Therefore, the grooved plug solves this problem by providing a groove in the approach portion to convert the axial load into rotational force. In each figure, 1 is a metal tube, 54 is a grooved plug having an approach portion on the front side and a parallel portion formed from the end point of the approach portion, and 6 is a rolled ball. Here, the core of the rolled ball 6 is 0, the point where this rolled ball contacts the outer periphery of the metal tube [J] is A, the intersection of the perpendicular to the rolled ball core O and the ball surface is B, and the point A is Δk is the horizontal component (X component) of the contact length between the outer periphery of the metal tube and the rolled ball between The horizontal component of the contact length (X
component) is ΔΩ. In addition, the point where the inner diameter part of the metal tube contacts the grooved plug is A, the starting point of forming the groove bottom of the grooved plug approach part is C, and the contact vertical component (X component) between point A and the point opening is (I). )y1 Vertical component between point C and point exit (X component)
Let be (Cb)y. In addition, in FIGS. 5 and 6, P represents the groove pitch. In order to form a defect-free inner groove, the point A where the rolled ball contacts the outer periphery of the metal tube should be located at the approach part of the grooved plug, so that the inner diameter of the metal tube is aligned with the above A.
Compression of the metal tube by the grooved plug and the rolled ball starts from the approach site corresponding to the point. That is, it satisfies Ix<Ax<X. Of course, since the rolled ball core 0 is located in the parallel part near the end point of the approach part of the grooved plug, the mouth x (Bx) is satisfied. , and the grooved plug approach part starting point C preferably satisfies 0.5≦(Iro)y/(Cro)y≦1.0, more preferably 0.7≦(Iro)y /CC
mouth) y≦1.0. Further, it is preferable that the ratio of horizontal contact components Δk and Δk where the rolled ball and the metal tube contact each other at the approach portion and the parallel portion of the grooved plug satisfy the following relationship: Δk/ΔC≧1. The basis for each of the above conditions is as follows. The present inventor has determined that Δk/Δl and tube expansion rate (Δe
/Δh), the relationship shown in FIG. 7 was obtained. In the figure, X marks are fin flaws with a depth of 1/100 mr11 or more, and O marks indicate fin flaws with a depth of 5/1000 m11 or more and 17100 mm or less (aivl
In the case of ltIt200x tail limit m (h depth), the O mark indicates the case where there is no flaw, and it can be seen that there is a preferable range (1) between the two, and a practical range (1). . Note that the tube expansion rate (Δe/Δh) is defined as shown in FIG. 12, and corresponds to Δe/Δh=(Iro)y/(Cro)y. Further, additional tests were conducted under the conditions of Δk/Δl=1/3 and Δe/Δh=0°7, and good results were obtained. From these, it was found that the more preferable conditions are Δk/Δa≧7/3 0.7≦(iro)y/CC口)y≦1.0. The reason why the degree of defect occurrence changes depending on the tube expansion ratio is considered to be as follows. When the tube expansion ratio is small, the tensile reaction force inside the metal tube becomes small, and the metal flow and the stress state inside the metal tube become close to that of the contracting tube rolling method, regardless of the contact point between the rolled ball and the metal tube. , fin flaws, and groove bottom defects are more likely to occur. Also,
In this case, the metal tube cannot have a sufficient wall thickness, making it difficult to form perfectly shaped fins. On the other hand, when the tube expansion rate is large, the tensile reaction force inside the metal tube becomes sufficiently large, so that the metal tube is grooved while being in close contact with the grooved plug. However, when the contact point A between the rolled ball and the outer periphery of the metal tube approaches the point (see Figure 5),
In the metal tube, almost no grooves are formed at the approach portion of the grooved plug, and the diameter is simply expanded, and most of the groove is processed at the parallel portion. In this case, since the grooving process is performed in a state similar to the tube reduction method, a slight entrainment phenomenon occurs in the metal flow at the fin part, and light wrinkle-like defects are also generated at the groove bottom, causing fin flaws and grooves. Bottom law is more likely to occur. On the other hand, when the contact point A between the rolled ball and the outer periphery of the metal tube approaches point A (see Figure 5), sufficient groove formation is performed at the same time as the diameter of the metal tube is expanded at this approach portion, so that the fin portion Since the metal flow becomes uniform and wrinkle-like defects are not generated at the bottom of the groove, good groove formation is achieved. Furthermore, when the expansion ratio is in the middle of the above, the tensile reaction force inside the metal tube is also of an intermediate degree, and from the above results, the closer the contact point A between the rolled ball and the outer circumference of the metal tube to point A, the better. It can be easily assumed that a good grooving process will be performed. The grooved plug is not particularly limited as long as it has a groove and at least an approach portion. For example, typical examples include a shape in which a groove is provided in a part of the approach portion as shown in FIG. 8, and a shape in which a groove is provided in the entire approach portion as shown in FIG.
These have parallel parts. The angle of the approach portion, ie, the approach half angle O, is preferably in the range of 5 to 13 degrees. If θ is less than 58, the approach part will be long and the frictional resistance with the metal tube will increase. If it exceeds 13 degrees, the approach surface pressure will increase, resulting in an increase in pulling resistance and it will be difficult to roll the metal tube with the rolling ball. Even when pressure is applied, the metal flows in the axial direction, making it impossible to make sufficient grooves and reducing the bottom wall thickness6.On the other hand, grooved plugs and lugs that do not have parallel parts can also be used.
For example, as shown in FIG. 10, a two-stage taper plug in which the first stage taper and the second stage taper are continuous with an appropriate curvature R is also possible. That is, in the tube expansion rolling method, as compared to the tube shrinking rolling method, the pulling resistance increases and a stress state occurs where the wall thickness decreases during tube expansion, making it difficult to groove. As a solution to this problem, there is usually a method of making the pipe wall before processing a little thicker than in the tube reduction compaction method, or a method of making the pipe wall before processing sufficiently thick using a grooved plug as shown in Figure 9. taken. Furthermore, in order to obtain a grooved tube of good quality without defects, the relative position of the rolled ball and the grooved plug should be set such that Δk/Δl≧1, preferably Δk/Δl≧77.
As mentioned above, it must be set to 3. In order to alleviate the above conditions and improve workability, the length of contact between the rolled ball and the metal tube should be increased. Specifically, as a countermeasure against this problem, as shown in FIG. 10, an angle θ2 of 0.2 to 1'' is attached to the parallel portion of the approach grooved plug shown in FIGS. 8 and 9. As a result, the contact length between the ball and the metal pipe behind the center of the rolled ball can be increased, and the expanded state can be maintained, so the expansion rate (Δe/Δh) = o, s, Δk
Even under boundary conditions such as /Δl=1, it is possible to fully utilize the advantages of the tube expansion rolling method and process a high-quality internally grooved tube. Furthermore, by using this grooved plug, the extraction speed can be increased without increasing the rotational speed of the rolling head, and productivity can be improved. Note that the approach half angle θ□ of the first taper of such a two-stage taper plug is preferably in the range of 5 to 13 degrees.
Multi-stage taper plugs with three or more stages are also possible. The first taper corresponds to the approach portion of the grooved plug shown in FIGS. 8 and 9. In the above-mentioned grooved plugs 4 of various shapes, the shapes and dimensions of the grooves or protrusions include those with various cross-sectional shapes such as chevron, triangle, trapezoid, etc., those with various depths ranging from PU groove to deep groove, and one-way spiral. It is possible to use grooves, spiral configurations that intersect in two directions, straight grooves, etc., and any combination of these as appropriate.In short, it is possible to mold various shapes required for design in each application field. It is possible. Of course, 2
In order to form spiral grooves that cross directions, spiral grooves in each direction may be sequentially formed using a pair of grooved plugs. On the other hand, in the above explanation, the case of a rolled ball was explained as the rolling member, but in the case of a rolled roller, the center of curvature at the end of the roller corresponds to the core of the rolled ball, so it is similarly applicable. . Note that the apparatus shown in FIG. 13 may be used as the apparatus used to carry out the present invention, but it is not limited to this, and other apparatus configurations used in the so-called pipe expansion and rolling method may also be used. be. For example, in the case of the device shown in FIG. 13, 2 is a first die with a fixed exit hole diameter, and 3 is a floating plug that does not have a bearing part, but these are not limited to the configuration shown in the figure. . That is, the first die 2 may have a variable exit hole diameter type or a one-rotation type.
If the plug is a plug without a bearing part as shown in the figure, the metal tube will become thinner when the diameter is reduced by cooperation with the first die 2, so the first die 2 should be a type with a fixed exit hole diameter It becomes easier to insert the grooved plug when the However, when the first die 2 is of a variable outlet type, even if a bearing part is used as the floating plug 3, the grooved plug cannot be inserted by expanding the outlet hole of the first die. It's easy to do. When the first die 2 has a fixed outlet hole diameter, the outlet hole diameter of the first die 2 is larger than the outer diameter of the grooved plug 4, so the grooved plug 4 passes through the first die 2 smoothly. The exit hole diameter of the first die 2 is designed to be equal to or slightly larger than ((outside diameter of the grooved plug 4) + (thickness of the metal pipe to be processed) x 2). It is preferable to facilitate the insertion of the tube, but when obtaining a larger expansion ratio,
The first die hole diameter can also be made small within a range that allows the grooved plug to pass through the first die. Furthermore, by using the floating plug 3 having no bearing part and the first die as a means for holding the grooved plug 4 in a predetermined position, a state close to empty drawing is achieved in which almost no wall thinning load occurs during the drawing process of the metal tube 1. The approach full angle θFP of the first die is appropriately designed from 0 SO to the full approach angle θFP of the floating plug, preferably 15 to 40.
It is also possible to minimize the drawing load by designing the metal tube so that θSD≧θFP and the work hardening of the metal tube is minimized to prevent deterioration in workability. After the start of machining, the state shown in FIG. 13 will be reached. However, if a plug without a bearing part is used as the floating plug 3, the floating plug 3 and the first die 2 will work together to When the metal tube passes through the first die exit hole, the metal tube is drawn to an outer diameter smaller than the inner diameter of the first die exit hole without reducing its wall thickness. The amount of narrowing can be changed by adjusting the angles of the first die 2 and the floating plug 3 (full approach angle θSD, θFP), so that the inner diameter portion of the metal tube after passing through the exit of the first die 2 becomes a groove. A range of 50% or more of the groove depth from the outer circumference of the attached plug 4, that is, 68
Preferably, the grooved plug tapers to contact at the approach portion at 766250%. If the inner diameter portion of the metal tube after passing through the exit of the first die 2 comes into contact with the grooved plug 4 with a narrowing amount of less than 50% of the groove depth, the effect of preforming the groove by the grooved plug 4 will not be obtained, and The amount of distortion in the radial direction of the pipe to be processed due to the rolling process by the rolling member 6 at the grooved plug portion is greater than the depth of the preformed groove, and the pipe to be processed and the grooved plug 4 may float. This is undesirable because it tends to cause internal defects. In this way, the grooved plug 4 is held at a predetermined position within the metal tube while maintaining the above-mentioned workability, and at the same time, the metal tube is continuously introduced into the rolling section while being expanded by the grooved plug 4, and is rolled. Groove forming is performed while rolling pressure processing is applied by the forming member 6. Finally, the grooved metal tube is passed through a diameter adjusting die 8 to adjust its diameter, thereby obtaining an internally grooved metal tube with predetermined dimensions. As the diameter-adjusting die, it is sufficient to use a fixed die, a rotating roll, etc., as appropriate, and either a fixed type or a rotary type may be used.

[Left below]

Next, one embodiment of the present invention will be described. Example G) Using the device shown in Fig. 13 (however, the positional relationship between the grooved plug 4 and the rolled ball 6 is as shown in Fig. 5),
Outer diameter 9.52++ from annealed phosphorus deoxidized copper metal pipe
A trapezoidal grooved tube with a wall thickness of 0.36 mm, a number of grooves of 60, and a lead angle of 18° was manufactured. First, lubricating oil or the like is injected into the metal tube 1 to be processed from the tube end, and a floating plug 3 with a full approach angle of 28 degrees rotatably connected by a tie rod 5, an outer diameter of 10.20 ts, and a groove depth of 0. A grooved plug 4 with a trapezoidal groove of 20 a+m and 60 grooves and an approach half angle of 9.5' was inserted. Next, after forming the eye portion by processing the tip of the tube end,
This mouth part is approached with a full angle of 28.5 degrees and an exit hole internally defined type (10,96 nus) first die 2 degrees expansion tube rolling section,
The pieces were sequentially passed through a diameter-adjusting die 8 and clamped to a drawing device (not shown) to complete the preparation work for grooving. Note that one work was carried out with the rotation of the rolled ball 6 stopped. After the preparation work was completed, the rolling ball 6 was revolved, the drawing device was driven, and drawing of the metal tube 1 was started under the processing conditions shown in Table 1. In addition, in the same table, the tubule ratio is determined by ID as shown in Fig. 11.
It is defined as PO/Di, and the expansion rate is Δ as shown in Figure 12.
It was defined as e/Δh. In addition, fin flaws and groove bottom knots are n
Judging by microscope (X200) IIJ* per number = 100, the percentage of occurrences with a depth of 5/1000 or more is expressed as the incidence rate, and the percentage of occurrences with a depth of 1/100 or more. is expressed as a defective rate within 0. As is clear from the table, in the case of tube reduction compaction method. Many fin defects occur, and the defective rate is extremely high.
Groove bottom knots are also occurring. On the other hand, in the case of the pipe expansion compaction method, when the pipe expansion rate is small, there is a strong tendency for fin flaws and groove bottom knots to occur regardless of the ratio of Δk/Δn, and when the pipe expansion ratio is medium, Δk/Δfi
If it is as small as = 2/8, almost the same results will be obtained when the tube expansion rate is small, but if it is as large as Δk/Δβ = 515.8/2, the occurrence of fin flaws and groove bottom disease will be observed, but the incidence rate will be lower. is significantly reduced. Furthermore, when the tube expansion rate is large, if it is as small as Δk/Δl=2/8, the effect of reducing the incidence of fin flaws and groove bottom disease can be obtained, and Δk/Δl=515.2/8.
When the value is increased, the reduction effect becomes more noticeable and can be completely eliminated. In addition, when the tube expansion rate is medium thick, neither of these defects occur. Furthermore, as a result of microscopic WA observation of the formed inner grooves, it was found that in the case of the tube reduction compaction method, fin flaws and groove bottom defects occurred as shown in Fig. 2 (a), and groove bottom defects ( As shown in b), many wrinkles appear. On the other hand, in the case of the tube expansion compaction method, in the case of A in the processing conditions column in Table 1, Fig. 4 (a)
In the case of ,C, slight fin flaws are observed as shown in the same figure (b), but in the case of H, there is no fin flaw as shown in the same figure (c), and as shown in the same figure (d) Similarly, there is no occurrence of sulcus disease. [Blank below] (Effects of the Invention) As detailed above, according to the present invention, the relative positions of the grooved plug and the rolling member are regulated to a specific relationship in the so-called pipe expansion rolling method, and the inner groove can be formed. Since I configured it to do this,
In particular, the occurrence of defects such as fin flaws and groove bottom knots can be significantly reduced or even eliminated, making it possible to manufacture high-quality internally grooved tubes.

[Brief explanation of the drawing]

Figure 1 is a diagram illustrating the concept of the fin formation mechanism in the grooved state by the tube reduction method, and Figure 2 is a micrograph showing the metal structure of the groove of the internally grooved tube obtained by the tube reduction method. So, (a) shows the cross section (X 200), and (b)
indicates the plane (X38) of the groove formation start part. Figure 3 is a diagram explaining the concept of the fin formation mechanism in the state of groove processing by the tube expansion and rolling method, and Figure 4 is a microscopic photograph showing the metal structure of the groove of the internally grooved tube obtained by the tube expansion and rolling method. (a) to (C) show the cross section, (d) shows the plane (X38) of the groove forming start part, and Fig. 5 and Fig. 6 show the inner groove formed by the pipe expansion rolling method according to the present invention. FIG. 3 is a cross-sectional explanatory diagram showing a processing state. FIG. 5 shows a case where a grooved plug having a groove in a part of the approach part is used, and FIG. 6 shows a case in which a grooved plug having a groove in the entire approach part is used. Figure 7 shows the pipe expansion rate (Δ
e/Δh) and the relative position of the rolled ball and the grooved plug. Figures 8 to 10 are diagrams showing the shape of the grooved plug. Figures 8(a) and 9 Figures (a) and 10 are longitudinal sectional views, and Figures 8 (b) and 9 (
b) are cross-sectional views seen from the X direction of FIGS. 8(a) and 9(a), respectively, and FIG. 11 shows the tube shrinkage ratio (1-D Pa / Di ), Figure 12 is a diagram explaining the pipe expansion rate (Δe/Δh
). Figure 13 is a diagram showing the internal groove machining state and equipment in the conventional tube expansion and rolling method, and Figure 14 is the grooved plug that is produced when thick-walled materials are rolled using the conventional tube expansion and rolling method shown in Figure 13. FIG. 3 is an explanatory diagram showing a rotation defect phenomenon. FIG. 15 is a diagram showing the internal groove machining state and apparatus in the tube reduction compaction method. DESCRIPTION OF SYMBOLS 1... Metal tube, 2... First die, 3... Floating plug, 4... Grooved plug, 5... Tie rod, 6... Rolled member (rolled ball or rolled roller)
, 7... Holding ring, 8... Diameter die, 9...
Groove forming part, 10... Grooved plug part where groove is not formed, ■... Unfilled area, ■... Uncrimped defect (fin flaw), ■... Wrinkle-like defect, ■... -Sulcus bottom node. Patent Applicant Kobe Steel Co., Ltd. Patent Attorney Takashi Nakamura Figure 1: Wheel Yunxuan-no-匈 Figure 3: Ball Fairness! 1-way visit 2° “[D-Yane-kata visit figure figure figure figure figure figure figure figure figure / noon figure] 0 figure figure figure figure figure

Claims (1)

[Scope of Claims] (1) The diameter of the metal tube is reduced using a drawing die and a floating plug, and then the inner surface of the metal tube is expanded and grooved using a rolling member supported by a retaining ring and a grooved plug. Further, in the method for grooving the inner surface of a metal tube, the diameter of the metal tube is adjusted using a diameter adjusting die, and the tube is continuously expanded by rolling and drawing, using a grooved plug having an approach portion at the front as the grooved plug, When the grooved plug and the rolling member work together to expand the diameter of the inner surface of the metal tube and form grooves, the rolling member applies pressure from the area where the inner diameter portion of the metal tube contacts the grooved plug approach portion. A method for forming internal grooves on a metal tube, characterized in that the internal grooves are formed while the metal tube is being grooved. (2) The method according to claim 1, wherein the rolled member is a rolled ball, and the rolled ball core is arranged in a parallel portion near the end point of the approach portion of the grooved plug. (3) The grooved plug and the rolled ball should be aligned so that the outer diameter of the metal tube and the rolled ball are in contact between the contact point between the inner diameter of the metal tube and the grooved plug and the end point of the grooved plug approach part. 3. The method according to claim 1, wherein the position is restricted. (4) Let Δk be the horizontal component of the contact length between the outer circumference of the metal tube and the rolled ball between the point where the outer diameter of the metal tube and the rolled ball start contact and the end point of the grooved plug approach part, and When the horizontal component of the contact length between the end point of the grooved plug approach part and the perpendicular line of the rolled ball core is Δl, Δk and Δl
4. The method according to claim 1, wherein the relative positions of the grooved plug and the rolled ball are regulated so that the ratio of Δk/Δl≧1 is satisfied. (5) Let y be the contact vertical component between the point A where the inner diameter part of the metal tube contacts the grooved plug and the end point B of the grooved plug approach part, and the starting point C of forming the groove bottom of the approach part of the grooved plug. When the vertical component of the end point b of the approach section is (Cb)y, the grooved plug and rolled ball should be adjusted to satisfy the following formula: 0.5≦(b)y/(Cb)y≦1.0. The method according to any one of claims 1 to 4, wherein the relative position of the is regulated. (6) The approach half angle of the approach part of the grooved plug is 5
6. A method according to any one of claims 1 to 5, wherein the angle is -13[deg.]. (7) When the grooved plug is a multi-step tapered type having no parallel portion, the first step taper portion is the approach portion, and the approach half angle is 5 to 13 degrees.Claims 1, 3 to 5
The method described in any of the above.